Photographic elements typically contain a light sensitive silver halide emulsion layer sensitive to blue light. A sensitizing dye is generally used to provide the desired sensitivity to blue light. Dyes used for this purpose tend to be water insoluble and are added to a silver halide emulsion in a water/alcohol solution. A problem that arises with this procedure is crystallization of the dye. Because of this, larger amounts of dye must be used to ensure the desired degree of sensitivity. Also crystallization of the dye poses difficulties in manufacture of photographic elements, e.g., plugging filters used to purify the emulsion prior to coating the emulsion on a support.
In the manufacture of photographic elements, the components used can result in undesirable results. For example, it is known to use certain gold compounds. However certain gold compounds react with gelatin which results in variability from batch to batch. Also, it is known to chemically sensitize silver halide using a gold compound that also contains sulfur. This limits the relative amounts of gold and sulfur to the stoichiometric amounts of the compound. It is desirable to vary the amount of gold versus sulfur to obtain the optimum sensitization for a particular photographic use.